To prevent intermediate or half fitting of a connector, there is conventionally known a method of reducing the force in insertion of one connector into another connector or providing a mechanism for doubling a force applied to a connector in insertion, thereby facilitating a coupling operation, a method of visually checking a half fit state or electrically detecting connections of contacts, or the like.
When the insertion force applied to the connector is reduced, the connectors are easily disconnected, and the method of doubling the force applied to the connector in insertion of detecting the electrical connections of the contacts complicates the connector structure or requires a special jig of a measurement equipment.